JP2009301920A - Nano chip emitter construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nanochip emitter construction method in which a method to arrange a single or a plurality of atoms at an emitter top end is achieved. <P>SOLUTION: High voltage to low voltage are applied in the order from the outside crystal surfaces to the inside crystal surfaces of a tungsten emitter 1 on an extraction electrode 5, and each time, electric field evaporation is carried out on the respective crystal surfaces. With this structure, by controlling the applied voltage on the emitter, an ion source having single or three pieces or six pieces of atoms arranged on [111] axis in (111) surface can be made. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a nanotip emitter, and more particularly to a method for producing a light source (nanotip emitter) emitted from a single atom or a plurality of atoms called a nanotip.

  As a charged particle beam light source, an electron beam uses FEG (field emission type) as a SERM (selective estrogen receptor agonist) light source, and a Ga liquid metal ion source is used for an ion beam. Such light sources are used in electron microscopes and FIB devices (focused ion beam devices).

  In recent years, research has been conducted on light sources emitted from single atoms or several atoms called nanotips. This light source is characterized in that it is several nm or less and the luminance is one digit higher than the conventional light source size of several tens of nm. Nanochips are expected to have a small light source size and higher brightness by producing fine protrusions of about several nanometers on an emitter having a normal tip diameter of several hundreds of nanometers and concentrating a high electric field on these fine protrusions. is there.

The emitter is heated under a high electric field (electrostatic field or negative electric field) to build up the crystal orientation, and fine projections are produced. Precious metals are deposited on the tip of the emitter, and FIM (field ion microscope) is used. In addition, a method for manufacturing a fine protrusion on the emitter by heating and a high electric field and a method for manufacturing a fine protrusion by etching the tip of the emitter by introducing nitrogen (N ₂ ) gas in FIM have been reported.

The present invention relates to a method for producing a nanotip by field evaporation using FIM, which is different from the above method.
The FIM described above will be described. FIM is called a field ion microscope. The sharpened emitter (about 200 nm) is cooled below the temperature of liquid nitrogen, a positive high voltage is applied to the emitter, and a rare gas is ^introduced at 10 ⁻³ Pa near the tip of the emitter. When introduced to some extent, the rare gas is ionized according to the atomic structure at the tip of the emitter, and each ion is accelerated to project the atomic structure at the tip of the emitter onto a fluorescent plate. Today, it is known as the cheapest and most easily available device for obtaining the highest magnification.

  By further reducing the tip of the emitter to several nanometers or less, it is possible to create a noble gas ion with a very small light source size and high brightness. It is the main point of. The present invention is to arrange a single atom or a plurality of atoms at the tip of the emitter in order to make the tip about several nanometers, which not only applies a high voltage to the emitter, One or a plurality of atoms are arranged at the tip of the emitter by controlling with a specific voltage for moving the atoms in the crystal plane.

  FIG. 6 is a diagram showing a general configuration of the FIM. In the figure, reference numeral 1 denotes an emitter that generates ions, and a tungsten (W) single crystal that is electropolished to a tip diameter of 20 nm or less is usually used. The emitter 1 is heated by a power source 2 and its surface is cleaned under an ultrahigh vacuum. Moreover, the emitter 1 is normally cooled below the liquid nitrogen temperature by a cooling device (not shown).

3 is a gas introduction tube, and helium (He) or nitrogen (N ₂ ) is used as the gas. A valve 4 adjusts the amount of gas introduced in the ultra-high vacuum, and is connected to a gas cylinder 4 'outside the vacuum. Reference numeral 5 denotes an extraction electrode. A high voltage is applied between the emitter 1 and the extraction electrode 5 through a power source 6, and gas ions ionized in the vicinity of the emitter are accelerated in the direction of the extraction electrode 5 to create an ion beam. Further, the emitter 1 and the extraction electrode 5 are biased by a common power source 7 and given ion beam energy.

  Reference numeral 8 denotes an anode, which is normally held at the ground potential. An ion beam detector 9 is mainly used for MCP (Multi Channel Plate). Reference numeral 10 denotes a fluorescent plate, and an ion beam incident on the MCP 9 generates a number of electrons, which are accelerated and collide with the fluorescent plate 10 to emit light, and the atomic structure at the tip of the emitter is projected. Reference numeral 11 denotes a mirror which has a structure in which the pattern of the ion beam on the fluorescent plate 10 can be observed by the human eye 13 outside the vacuum via the observation window. The amount of the ion beam emitted from the emitter 1 and the emission pattern Used for observation.

  In the use in the present invention, the three parts of the MCP 9, the fluorescent plate 10 and the mirror 11 have an integral structure. After observing the pattern, these parts are removed from the light source from outside the vacuum, and the center ( The structure is such that a bright beam of (111) plane can enter a lens below or an ion optical lens system which is a deflection system. The atomic structure at the tip of the emitter can be observed using such an FIM apparatus.

  FIG. 7 is a diagram showing a crystal plane according to a ball model of a tungsten single crystal. (A) shows the crystal plane when viewed from the direction of the axis [111] (perpendicular to the paper surface) perpendicular to the (111) plane, and corresponds to the case of observation from the sharp tip direction of the tungsten emitter used. b) shows the side surface viewed from the (110) plane side, and corresponds to the case where the tip of the emitter is observed from the lateral direction.

  The [111] axis is surrounded by three {211} planes, that is, (211), (121), and (112), and the three outer {110} planes, that is, (110), (101), (011). ) Is surrounded. Although not shown here, it can be seen that three {221} planes and three {335} planes are observed between the [111] and {211} planes in the FIM image.

  FIG. 8 is a diagram showing the arrangement of atoms on the tungsten (111) plane surrounded by three {211} planes. The axis [111] of the (111) plane is perpendicular to the page, with one atom on the top terrace, three atoms on the bottom terrace below it, and even below it. It can be seen that 10 atoms are located in the third layer. When a positive high voltage is applied to the emitter, the direction of the electric field is from the bottom to the top of the page.

  Therefore, the 10 atoms in the third layer described above, especially the 3 atoms at the apex of the triangle, have a stronger electric field than the other atoms, so they are immediately released into the vacuum as 10 particles. It is not observed but is observed as 6 particles. That is, this means that if for some reason the top single atom flies away somewhere, by controlling the electric field strength from the outside, one atom from the second layer below it is Similarly, when three atoms in the second layer are missing, it is expected that the atoms in the third layer below it can be moved to the second layer and supplemented. This means that the atomic arrangement at the tip of the emitter can be correctly aligned by optimally controlling the strength of the electric field from the outside.

  In this type of conventional apparatus, a voltage for evaporating the tip of the emitter is applied between the emitter and the extraction electrode with a relatively low first pressure in the ionization chamber, and then the extraction voltage is lowered to reduce the ion A technique is known in which a voltage at which the maximum angular current density of a beam is obtained is detected, and then an extraction voltage is set to the voltage (see, for example, Patent Document 1).

  In addition, a technique is known in which the extraction voltage is increased to field evaporate the tip of the emitter, the field voltage is evaporated at this voltage, the extraction voltage is lowered, and ionization is concentrated on the (111) plane of the emitter tip ( For example, see Patent Document 2).

And an emitter, an emitter cooling means, an extraction electrode, a means for introducing a gas to be ionized around the emitter, and a means for applying a pulse voltage superimposed on a DC high voltage between the emitter and the extraction electrode. A technique is known (for example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 7-272651 (paragraphs 0023 to 0028, FIG. 5) JP-A-7-192669 (paragraphs 0010 to 0018, FIG. 3) JP-A 64-10548 (page 2, upper right column, line 14 to page 3, upper left column, line 18, FIGS. 1 to 3)

  In the conventional technique, the emitter is heated under a high electric field to build up the crystal orientation, and fine protrusions are produced, or noble metal is deposited or plated on the tip of the emitter, and heating and high electric field are applied using FIM. In this case, a method of manufacturing a fine protrusion on the emitter, a method of manufacturing a fine protrusion by etching the tip of the emitter by introducing nitrogen gas in the FIM, and the like can be considered.

  In the prior art, when the emitter is heated, the temperature control is complicated, and the buildup of the crystal orientation depends on the quality of the vacuum residual gas. Also, in the deposition and plating of precious metals, the deposition and plating of several atomic layers is extremely difficult, and in particular, in the case of plating, residues such as plating solution become contamination in ultra-high vacuum, which is highly reproducible. There's a problem. Further, the etching of nitrogen gas has a problem that it takes a long time for etching.

  Further, in order to attach a single atom or a plurality of atoms to the tip of the emitter using field evaporation by FIM, a high voltage must be applied with reproducibility and extremely high setting accuracy. In the creation of a nanotip emitter using field evaporation, a unique high voltage corresponding to each crystal plane is applied to align atoms on each crystal plane.

  The application of this high voltage needs to be optimally controlled so as to move and rearrange the atoms on the crystal plane. If the voltage value is too high, atoms are released into the vacuum by field evaporation. In addition, if the voltage is too low, there is a problem that relocation within the crystal plane cannot be performed.

  In this way, by controlling the electric field strength, the field evaporation is controlled by applying a strong electric field, and the arrangement of atoms is controlled without releasing atoms caused by a weak electric field to the outside of the vacuum, so that the maximum electric field emission is obtained. It is necessary to control with lowering. Moreover, this process must be performed with good reproducibility and accuracy.

  Currently, the high voltage is set by manually manipulating the high voltage and observing the emission pattern on the MCP (microchannel plate) while checking how much the target crystal plane is evaporated. It is carried out. The state of field evaporation can be predicted from the fact that the contrast of the target crystal plane in the observed image is remarkably lowered, or the state in which atoms frequently move around.

  However, in the observation during field evaporation, even if the rearrangement of atoms can be predicted, it cannot be accurately determined whether or not the atoms have been correctly rearranged. An FIM image is observed. That is, at present, an FIM image is observed at an arbitrary high voltage Vo, and the target crystal plane is subjected to field evaporation. Therefore, field evaporation is performed for an arbitrary time at a voltage of Vo + ΔV1 obtained by increasing the high voltage by ΔV1, and thereafter Then, the voltage is returned to Vo again, and it is confirmed whether or not the rearrangement of atoms has been performed. If the rearrangement has not been performed, electric field evaporation is performed again by increasing ΔV1 or ΔV2, and then confirming again. Therefore, the voltage Vo is returned to the observation. In order to optimize the emission from atoms, the normal Vo voltage must be further lowered.

These operations are repeated as necessary until the desired rearrangement is performed. This is extremely troublesome for humans who operate the apparatus.
The present invention has been made in view of such a problem. First, a single or a plurality of atoms are finally formed at the tip of an emitter by setting and controlling a high voltage applied voltage according to each crystal plane. The second purpose is to superimpose ΔV on the high voltage of Vo, set the width of ΔV arbitrarily, and change with time to perform field evaporation, and to rearrange the atoms. The purpose is to realize a method to make sure.

  (1) According to the first aspect of the invention, a high voltage and a low voltage are sequentially applied to the extraction electrode from the outer crystal face to the inner crystal face of the tungsten emitter, and field evaporation is performed on each crystal face each time. Features.

(2) The invention described in claim 2 is characterized in that, in the case of performing field evaporation by sequentially applying an appropriate extraction voltage to each crystal plane of a tungsten emitter, the following steps are performed.
1) A voltage V1 is applied to the tungsten emitter to cause field evaporation of atoms on the crystal plane (110). 2) A voltage V2 (<V1) is applied to the tungsten emitter to cause field evaporation of atoms on the crystal plane (211). 3) A voltage V3 (<V2) is applied to the tungsten emitter, and field evaporation of atoms on the crystal plane (221) is performed. 4) A voltage V4 (<V3) is applied to the tungsten emitter, and atoms of the crystal plane (111) are applied. Conduct field evaporation 5) Apply voltage V5 (<V4) to tungsten emitter and perform field evaporation of atoms on crystal plane (111) 6) Apply voltage V6 (<V5) to tungsten emitter to crystal plane (111 (3) In the invention according to claim 3, the extraction voltage to the tungsten emitter is swept and applied to the extraction electrode at an arbitrary time width. It is characterized in that atom rearrangement based on optimum field evaporation is performed.

  (4) According to the invention of claim 4, the application of the extraction voltage to the extraction electrode of the tungsten emitter is changed from Vo + ΔV to Vo−ΔV, and the state of Vo−ΔV is maintained for a predetermined time in the changed state. Repeatedly, atomic rearrangement is performed by field evaporation at Vo + ΔV, and the arrangement of atoms constituting the emitter is stabilized by holding in a state of Vo−ΔV for a predetermined time.

  (5) The invention according to claim 5 is the invention according to claim 4, wherein the emission current to the extraction electrode is obtained by measuring the emission current at the time of sweep, and the extraction voltage power source is controlled from the control device to control Vo + ΔV and Vo−ΔV. It is characterized in that it is automatically applied to the extraction electrode to stabilize the arrangement of atoms.

  (1) According to the first aspect of the present invention, a single or a plurality of atoms can be finally arranged at the tip of the emitter by setting and controlling a high voltage applied voltage adapted to each crystal plane. .

   (2) According to the invention described in claim 2, the single or plural atoms are finally arranged at the tip of the emitter by gradually lowering the high voltage applied voltage corresponding to each crystal plane. be able to.

  (3) According to the invention described in claim 3, the amount of voltage change is superimposed on a reference high voltage, the width of the amount of voltage change is arbitrarily set, and the time is changed with time to perform field evaporation, so Arrangement can be ensured.

   (4) According to the invention of claim 4, the application of the extraction voltage to the extraction electrode of the tungsten emitter is changed from Vo + ΔV to Vo−ΔV, and the state of Vo−ΔV is held for a predetermined time in the changed state. By repeating this process, the rearrangement of atoms can be ensured.

  (5) According to the invention described in claim 5, the rearrangement of atoms of the tungsten emitter can be automatically performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
An embodiment of the method of the present invention will be described using the FIM (field ion microscope) shown in FIG. Hereinafter, tungsten is expressed as W.

1) When a W (111) emitter having a tip diameter of about 200 nm is evacuated in an ultrahigh vacuum, He gas is introduced at about 10 ⁻³ Pa, and a positive high voltage is gradually applied to the emitter 1. The adsorbed gas molecules adsorbed on are released by the electric field, and random spots are displayed on the MCP 9. This is generally called field desorption.

  When the applied voltage is further increased, atoms in the emitter 1 move due to the action of a strong electric field from the outside, and atom migration (movement) is performed. If there is a defect in the crystal, it can be corrected by this action. Furthermore, by increasing the applied voltage, atoms that have moved around in the crystal are released from the emitter 1 into the vacuum by this strong external electric field, and tungsten atoms are evaporated in a field.

  In this way, by controlling the electric field in the vicinity of the emitter by applying a high voltage, it is possible to release the adsorbate on the emitter surface, rearrange the atoms in the crystal plane, or evaporate the atoms constituting the emitter 1. it can. These series of processes are observed as emission patterns on the MCP 9. While observing the emission patterns on the MCP, the atoms on each crystal plane of the emitter 1 already shown are subjected to field evaporation and each crystal at a specific high voltage value. By controlling the migration of atoms in the plane, it is possible to finally arrange a single atom of tungsten, three atoms, or six atoms on the [111] axis.

  2) First, in order to align the atoms on the {110} plane described above, the voltage V1 at which the atoms on the {110} plane perform field evaporation is applied. When field evaporation is performed, atoms on the {110} plane move violently on the MCP 9, and atoms on the outer periphery of each {110} plane move toward the center of the {110} plane and come to the center. The state of being released into the vacuum can be observed. While making this observation, the voltage V1 is set, and as a result, the atoms on the {110} plane are aligned.

  FIG. 1 is a view showing an FIM image according to the present invention, and (A) to (F) are shown. This figure is a diagram showing an example of a main screen in the display screen displayed on the display in one embodiment of the present invention as a photograph of a halftone image (the same applies to FIGS. 2 and 9). FIG. 1A is an FIM image observed by lowering the voltage to 21 KV after performing field evaporation on the {110} plane at V1 = 23 KV. It can be seen that the {110} plane is clearly identified. At the same time, the region of the {211} plane is observed in a dazzling manner, which indicates that the {211} plane is being evaporated in the current V2 = 21 KV.

  3) Next, in order to align atoms on the {211} plane inside the {110} plane, a voltage V2 lower than the previous V1 is applied, the field evaporation of the {211} plane is performed, and the {211} plane Align atoms at. In this case as well, while observing that the atoms on the outer periphery of each {211} plane move toward the center of the {211} plane on the MCP 9 as described in 2) and then released to the outside of the vacuum, Set the voltage V2.

  In FIG. 1A shown above, since the voltage is set to 21 KV, which is lower than the previous voltage V1, the field evaporation on the {211} plane has already started. It can be easily judged from the fact that it is observed as if itchy.

  4) Similarly, a voltage V3 lower than the previous V2 is applied, and field evaporation of the {221} plane located inside the previous {211} plane is performed. The voltage of V3 can be set to an optimum voltage value by observing the pattern on the MCP 9 as in the case of the hand and the fact that the region of the {221} plane appears blurred by field evaporation. FIG. 1B is an FIM image observed at V3 = 17 KV. Since the {211} plane is already cleared and the area of the {221} plane is blurred, the electric field at the {221} plane is shown. It can be seen that evaporation is in progress.

  5) Further, the voltage V4 lower than the previous applied voltage V3 is applied, and the field evaporation of the (111) plane atoms is performed in the same manner as described above. As a result, the voltage V4 is set so that a single, three, or even six atoms are arranged on the (111) plane shown in FIG. (C) in FIG. 1 is an FIM image in which V4 is set to 14 KV and field evaporation of the (111) plane is performed. Even in this case, the optimum voltage V4 is set while observing the FIM image on the MCP 9.

FIG. 1D shows the FIM image obtained after field evaporation at a voltage of 14 KV, and it can be seen that 6 atoms are observed on the (111) plane.
6) Further, by applying a voltage V5 lower than the previous applied voltage V4, the upper three atoms of the previous six atoms can be similarly created by the same method. FIG. 1E is an FIM image obtained after field evaporation at a voltage of 13 KV, and the three atomic images shown in FIG. 8 are observed.

  7) Furthermore, a single atom can be arranged by setting a voltage V6 lower than the previous applied voltage V5. FIG. 1F shows a single atom image obtained after field evaporation at 12 KV.

  8) In this way, by sequentially changing the voltage applied to the tungsten emitter and performing field evaporation, atoms on each crystal plane of the emitter 1 migrate to the tip of the emitter, and at a single atom or multiple atom level It is possible to regenerate damaged emitters while creating a light source of charged particles.

As described above, according to the first embodiment, a single or a plurality of atoms can be finally arranged at the tip of the emitter by setting and controlling the high voltage applied voltage according to each crystal plane. Further, by gradually lowering the high voltage applied voltage corresponding to each crystal plane, it is possible to finally arrange single or plural atoms at the tip of the emitter.
(Second Embodiment)
FIG. 9 is a diagram showing an FIM image by He gas in a (111) -oriented single crystal emitter. FIG. 9A is an ideal FIM image with He gas in a single crystal emitter of tungsten (111) orientation. Three atoms are arranged in the central (111) crystal orientation plane, a large number of atoms with three {221} crystal orientations on the outside, and a large number of atoms with three {211} crystal orientations on the outside as well However, it is also shown that a large number of atoms of three {110} crystal orientations surround the outside.

  Of particular note is the number of atoms on the (111) crystal plane located at the emitter tip, and in the physical ideal state, the emitter tip is one on the top surface, as shown in FIG. Three are arranged in the second lower layer, and ten are arranged in the third lower layer. An object of the present invention is to use single or three atoms arranged on the (111) plane as an ion light source having an extremely small light source size and extremely high luminance.

  However, in a normal FIM experiment, as described above, single or three atoms are not necessarily arranged on the top of the (111) plane, the voltage application state in field evaporation, the vacuum in the vicinity of the emitter. As shown in FIG. 9B, the top and second layer atoms are blown away by field evaporation, and the third and fourth layer atoms are the most, as shown in FIG. 9B. Often, the structure is arranged on the upper surface.

  FIG. 9B shows a pattern with the same emitter, but since the pattern was observed at different times, the pattern was rotated by shifting the position of the observation camera, and the magnification was also shown differently. In such a case, when these are used as the light source, the light source size is increased and the luminance is greatly reduced, so that the optimum state for use cannot be obtained. Thus, in order to use as a light source, it is extremely important to arrange single or three atoms on the (111) plane with good reproducibility. Therefore, the gist of the present invention is to perform rearrangement of atoms by delicately and precisely controlling the voltage applied to the emitter. In the present invention, the atomic structure at the tip of the emitter is observed using this FIM apparatus, and the applied voltage is controlled minutely to control the arrangement of atoms at the tip.

  FIG. 2 is a diagram showing a series of results in which the extraction voltage is controlled so that three atoms are arranged on the top of the (111) plane. The extraction voltage corresponding to each pattern of FIG. 2 is shown in the voltage application graph of FIG. FIG. 3 is a diagram showing how the extraction voltage is applied. The horizontal axis is time, and the vertical axis is the extraction voltage.

  FIG. 2A is an FIM image obtained with an extraction voltage of 12 KV. In the center of (111) indicated by a circle, at least three or more atoms are observed, but the number is not clear. This corresponds to the (A) state of Vo = 12 KV in FIG. FIG. 2B is an FIM image when the extraction voltage is further increased to 12.65 KV. The atoms in the center of (111) move around due to a strong electric field, and the center is blurred. I understand. This corresponds to the application of an electric field at the voltage shown in FIG.

  After the end of this process, the result of FIM observation at the position of (C) in FIG. 3 where the extraction voltage was returned to the original 12 KV value is shown in (C) of FIG. It can be seen that four atoms are gathered in the center of. In order to place three atoms on (111), a strong electric field must be applied again. The voltage in FIG. 3D is increased to 12.7 KV, and a stronger electric field is applied.

  This state corresponds to (D) in FIG. 2, and the center of (111) is observed in a blurred manner as before, and atoms are moved or field evaporation is performed due to strong voltage application. I understand that. The FIM image shown in (E) of FIG. 3 when observed by returning to a voltage of 12 KV is shown in (E) of FIG. 2, and a triangular structure is observed in the center of (111). It is expected that a trimmer of three atoms has been formed.

  Next, when the voltage is lowered to 11.5 KV as shown in FIG. 3F, field evaporation and atom movement no longer occur, and as shown in FIG. Three atoms are clearly observed in the center. Further, in 9.53 KV in the state as shown in FIG. 3G, the luminance of the three atoms on the (111) plane shown in FIG. In comparison, it is markedly brighter.

  As described above, in a nanotip emitter formed by rearranging single or plural atoms, accurate control of applied voltage, reproducibility, and vertical characteristics of applied voltage are extremely important in order to accurately control electric field application. Become. According to this embodiment, the amount of voltage change is superimposed on a reference high voltage, the width of the amount of voltage change is set arbitrarily, and is changed with time to perform field evaporation in a predetermined time width, Relocation can be ensured.

  Further, since the application of the extraction voltage to the extraction electrode of the tungsten emitter is changed from Vo + ΔV to Vo−ΔV, and the state of Vo−ΔV is maintained for a predetermined time in the changed state, the atomic rearrangement is performed. The rearrangement of atoms can be ensured.

  FIG. 4 is a diagram showing a main part of one embodiment of the present invention. The same components as those in FIG. 6 are denoted by the same reference numerals. In the figure, 1 is an emitter, 5 is an extraction electrode, 6 is an extraction voltage power source for applying an extraction voltage to the extraction electrode 5, 20 is a personal computer (PC) for controlling the extraction voltage power source 6, and 22 is an emission from the emitter 1. An emission current detector 21 for detecting current is an ammeter that receives the output of the emission current detector 22 and measures the emission current, and the output is notified to the PC 20. The operation of the apparatus configured as described above will be described as follows.

  Ions are accelerated by an extraction voltage power source 6 applied to the extraction electrode 5 to emit an ion beam. The emission current from the (111) plane is detected by the emission current detector 22 and connected to the PC 20 through the ammeter 21. The extraction voltage power source 6 is controlled by the personal computer 20, the emission current value by the extraction voltage is recorded, and the extraction voltage is controlled so as to obtain the optimum emission.

  FIG. 5 is a diagram showing how the extraction voltage control is performed. The horizontal axis is time, and the vertical axis is the extraction voltage. After applying the voltage Vo to the clean (111) emitter, the voltage is increased by a voltage ΔV1 in a predesignated ascending step to Vo + ΔV1, causing atoms to move on the (111) plane, and then the voltage is The emission current Io is measured in this state by lowering it by the designated lowering step ΔV2 to Vo + ΔV1−ΔV2. Specifically, the emission current detector 22 (see FIG. 4) detects the emission current.

  The PC 20 compares the emission current Io with a target emission current Ik designated in advance. If Io is smaller than Ik, it is further lowered by ΔV2, and the emission current Io is measured in the same manner and compared with Ik. Repeat until a predetermined number of times N until Io becomes Ik.

  When the target Ik cannot be obtained, the process returns to the original state, and when the voltage is increased to move the atom, the voltage is set to Vo + ΔV1, and thereafter the voltage decrease and the measurement and comparison of Io are repeated in the same manner. By performing such a control operation, the rearrangement of atoms of the tungsten emitter can be performed automatically.

  As described above, according to the present invention, electric field evaporation is performed by adjusting the voltage applied to the emitter to each crystal plane, the emitter surface is cleaned, and atoms are rearranged in each crystal plane. The ion source can have a single, three, or six atoms arranged on the [111] axis in the (111) plane.

  In addition, when placing atoms at the tip of the emitter, the external electric field strength is controlled accurately and with good reproducibility, and in the process of atom movement in the crystal and field evaporation with a stronger electric field, a high voltage can be arbitrarily set. By performing electrical scanning within the range of the width, optimal field evaporation and atom rearrangement can be realized, and the maximum emission value can be easily obtained.

It is a figure which shows the FIM image by this invention. It is a figure which shows a series of results which controlled extraction voltage so that three atoms may be arrange | positioned at the vertex of a (111) plane. It is a figure which shows the mode of extraction voltage application. It is a figure which shows the principal part of one embodiment of this invention. It is a figure which shows the mode of extraction voltage control. It is a figure which shows the general structure of FIM. It is a figure which shows the crystal plane by the ball | bowl model of a tungsten single crystal. It is the figure which showed the arrangement | sequence of the atom of the (111) surface enclosed by three {211} surfaces. It is a figure which shows the FIM image by He gas in the single crystal emitter of (111) direction.

Explanation of symbols

1 Emitter 5 Extraction electrode 6 Extraction voltage power supply 20 Personal computer (PC)
21 Ammeter 22 Emission current detector

Claims (5)

  A method for producing a nanotip emitter, wherein a high voltage and a low voltage are sequentially applied to an extraction electrode from an outer crystal face to an inner crystal face of a tungsten emitter, and field evaporation is performed on each crystal face each time. The method for producing a nanotip emitter according to claim 1, wherein the field evaporation is performed by sequentially applying an appropriate extraction voltage to each crystal plane of the tungsten emitter in the following steps.
1) A voltage V1 is applied to the tungsten emitter to cause field evaporation of atoms on the crystal plane (110). 2) A voltage V2 (<V1) is applied to the tungsten emitter to cause field evaporation of atoms on the crystal plane (211). 3) A voltage V3 (<V2) is applied to the tungsten emitter, and field evaporation of atoms on the crystal plane (221) is performed. 4) A voltage V4 (<V3) is applied to the tungsten emitter, and atoms of the crystal plane (111) are applied. Conduct field evaporation 5) Apply voltage V5 (<V4) to tungsten emitter and perform field evaporation of atoms on crystal plane (111) 6) Apply voltage V6 (<V5) to tungsten emitter to crystal plane (111 ) Field evaporation of atoms   A method for producing a nanotip emitter, characterized in that an atom rearrangement based on an optimum field evaporation is performed by sweeping and applying an extraction voltage to a tungsten emitter at an arbitrary time width to an extraction electrode.   The application of the extraction voltage to the extraction electrode of the tungsten emitter is changed from Vo + ΔV to Vo−ΔV, and the state of Vo−ΔV is maintained for a predetermined time in the changed state. 4. The method for producing a nanotip emitter according to claim 3, wherein the arrangement of atoms constituting the emitter is stabilized by performing and maintaining for a predetermined time in a state of Vo−ΔV.   5. The emission current to the extraction electrode is obtained by measuring the emission current at the time of sweeping, and the control device controls the extraction voltage power source to automatically apply Vo + ΔV and Vo−ΔV to the extraction electrode. A method for producing a nanotip emitter, characterized in that the arrangement is stabilized.